How can I force my machine to use only the first processor?

A. If you want to use only one processor of a multiprocessor machine, you can use the numproc boot.ini switch (see What switches can be used in boot.ini? for more information about numproc and other boot.ini switches).

Start a command session (Start, Run, cmd.exe).

Go to the root of the C drive.

Use the following command to modify the boot.ini file so it is not a system file, not hidden, and not read-only:

C:\> attrib boot.ini -r -s -h

Open the file in Notepad:

C:\> notepad boot.ini

Locate the entry that starts the OS and add /numproc=1 to the end. For example,